A repairman purchased several furnace-blower motors for a total cost of $150. If his cost per motor had been $5 less, he could have purchased 1 additional motor. How many motors did he buy at the regular rate?

Answer 1

This is similar to what I just answered earlier.

x = total cost
y= # of motors bought

150 = x*y

solving for y:

150/y= x <--- (1)

now we know:
150=(x-2)*(1+y) <--- (2)

substitute using (2) and (1) we get :

150=((150/y)-5)*(1+y)

30 = y^2+y

y^2+y -30= 0

(y+6)(y-5)=0

y = -6, 5

real solution is 5, can't buy negative engines..